Digital clock

ABSTRACT

A DIRECT READING CLOCK PROVIDED WITH A UNITARILY MOLDED HOUR DRUM HAVING A NUMBER OF MULTI-FACED NUMERAL DISPLAY BODIES EQUISPACED ALONG ITS PERIPHERY. A STATIONARY APRON OVERHANGS A REDUCED PORTION OF THE BODIES TO MAINTAIN ORIENTATION OF THE BODIES. A STEPPING PAWL IS FORMED ON THE APRON AT A PREDETERMINED POSITION TO ENGAGE EACH BODY IN TURN AT THAT POSITION TO ROTATE THE BODY AND EXPOSED A DIFFERENT SURFACE THEREOF.

Nov.v2, 1971 o. OBERGFELL ETAL 3,616,642

DIGITAL CLOCK '3 Sheets-Sheet 1 Filed A ril 28. 1970 Oskar Obergfoll GUnrer Humme! INVENTORS Attomy Nov 2, 1971 o. OBERGFELL F-TAL I 3,615.54:

DIGITAL CLOCK Filed April 28, 1970 3 Sheets-Sheet 2 Oskar Obergfell GUnfer Hummel IN V EN TORS.

Attorney Nov; 2, 1971 0.0BERGFELL EIAL v 3,616,642

DIGITAL CLOCK Fild April 28, 1070 3 Sheets-Sheet 3 .Oskar Oberg fell Giinfer Humme! INVENTORS.

Attorney United States Patent Oflice Patented Nov. 2., 1971 ABSTRACT OF THE DISCLOSURE A direct reading clock provided with a unitarily molded hour drum having a number of multi-faced numeral display bodies equispaced along its periphery. A stationary apron overhangs a reduced portion of the bodies to maintain orientation of the bodies. A stepping pawl is formed on the apron at a predetermined position to engage each body in turn at that position to rotate the body and exposed a different surface thereof.

FIELD OF THE INVENTION Our present invention relates to a so-called digital clock, digital-display arrangement, numeral indicator or other device of the direct-reading type wherein a succession of digits is to be displayed at, for example, a window of the device.

BACKGROUND OF THE INVENTION Direct-reading instruments and devices of various forms have been proposed heretofore and generally comprise a display window through which numerals may be viewed. Such instruments include counters, calculating devices and, especially in recent years, so-called digital clocks in which, in place of hands cooperating with a clock face, time is displayed in the form of numerals representing hours, minutes and seconds. Digital calendars have also been provided to represent days, months and/or years, and combined calendar clocks are also available to indicate date and time together. While, for convenience, reference will be made herein to digital clocks, it should be noted that such reference is to a preferred embodiment only, since the principles involved are applicable also to the other digital-display arrangements mentioned above.

Consequently, the present invention is directed to direct-reading clocks in which the absolute time, e.g. as in an alarm clock, or relative time, e.g. as in an elapsedtime indicator, is displayed at a dial face in terms of appropriate time units, e.g. seconds only, minutes and seconds only, and hours, minutes and seconds, or fractions of any particular time period. It has been the practice heretofore, with such direct-reading clocks, to provide one or more drums rotatable about a common axis and carrying on their periphery indicia representing the time period of interest. An alternative construction makes use of a multiplicity of flaps, carrying the indicia and shifted into place adjacent a display window. Flap arrangements present problems in mounting and actuating the numerals and in stepping the device as may be required for the resetting to Zero of the elapsed time indicator or the adjustment of a real-time clock.

Drum-type digital clocks have other difiiculties, particularly based upon the problem of displaying a large number of numerals along the periphery of a drum, providing each numeral of sufficient size as to be easily read,

and maintaining the overall dimensions of the device with in reasonable limits. For example, a drum adapted to display the minutes on a time-piece may require 60 individual numerals, as may the second drum. If each numeral is to have a height of about 13 mm., as is reasonable for viewing convenience, the circumference of the drum must be at least 60 x 13 mm. and the drum must have a diameter of A drum of this diameter could not be conveniently received in household, commercial or industrial instruments. Hence, it has been proposed to display minutes, seconds, for example, each upon two drums, the right-hand drum bearing units designations (1, 2 0) while the left-hand drum represents the tens place and may bear the numerals 0, 1 5.

Difliculties are encountered, however, when the hour indication is considered. For example, if it is assumed that the clock is to display a 24-hour time scale, either a single drum with 24 indicia and of a minimum diameter of must be employed, or two drums, with 2 and 4 indicia, respectively, may be used. The forming technique yields too large a drum while the latter alternative has the disadvantage that, at the conclusion of each cycle, each drum must be rotated through a relatively large unused arc to reset it for the next cycle. The mechanisms reqiured for this purpose are unduly complex and hence 24-hour clocks have been avoided, hours indications have been omitted from digital clocks or the structures made so complex or unwieldly as to be undesirable.

OBJECTS OF THE INVENTION It is, therefore, the principal object of the present invention to provide an improved direct-reading device of the digital-display type which is compact, inexpensive and yet provides numerals of sufficient size as to permit easy viewing.

Another object of this invention is to provide a digitaldisplay arrangement having the advantages of drum-type systems and yet providing both a large number of numerals and relatively large numerals to facilitate viewing while nevertheless simplifying the structure.

Still another object of the invention is to provide a digital clock having improved means for displaying integers.

A more specific object of this invention is to provide a digital-display clock which avoids the disadvantages of earlier systems and yet enables the portrayal of a 24- hour period using a drum of convenient diameter.

SUMMARY OF THE INVENTION These objects and others which will become apparent hereinafter are attained, in accordance with the .present invention, in a digital-display or direct-reading instrument having drum-type numeral-display means including at least one display drum for the portrayal of a numbers or numerals along the periphery of the drum. According to this invention, a rotatable carrier is formed with a plurality of individual numeral-carrying members equispaced along its periphery so that each member may be rotated through a fraction of a full revolution about its axis during each revolution b of the drum. Such members are provided, according to the invention, each with c numerals displayed thereon such that a=b c. For each rotation of the drum, each of the numeral-display members is rotated through an arc fraction 1/ c of the peripheral extent of the member or circumference or through an increment of angle of 360/ C. To display the entire numeral bank of a numerals, the drum is rotated through c revolutions.

According to a more specific feature of the invention, the display device is a direct-reading clock of the digital type wherein hour, minute and second drums are provided, the housing of the unit being formed with a window displaying a limited portion of the periphery of each drum. At least the hour drum carries a plurality of polygonal members equispaced along its periphery and rotatable about axes parallel to the axis of rotation of the drum while means is provided such that, upon each full revolution of the drum, the b members are each rotated through l/c of a full revolution and a=24 for the 24- hour period of the clock. In this construction, it has been found to be advantageous to provide eight individual members (b=8) such that each has three display numerals or sides (c=3).

According to a more specific feature of the invention, the means for stepping the drum or its members includes a pawl arrangement positioned along at least one side of the drum and carrying a finger engageable with the individual members as the drum is rotated therepast to displace, in a sense counter to the rotational sense of the drum, each of the individual members carried along its periphery.

The drum, in turn, may be composed of synthetic resin and may be constituted as a spool with a shank unitarily formed with a pair of lateral disks having aligned openings receiving studs of the individual members such that these studs may be inserted and removed by a slight lateral deflection of the disks.

DESCRIPTION OF THE DRAWING The above and other objects, features and advantages of the present invention will become more readily apparent front the following description reference being made to the accompanying drawing in which:

FIG. 1 is an elevational view of a digital clock embodying the present invention;

FIG. 2 is a side view thereof;

FIG. 3 is a schematic end view, taken in a plane perpendicular to the axis of rotation of the hour drum, of a 24- hour display wheel according to the invention, illustrating its relationship with the display window of the clock.

FIG. 3A is an elevational view of this wheel;

FIG. 4 is a view similar to FIG. 3 but drawn to enlarged scale and illustrating additional parts of the drum;

FIG. 5 is a side view of the drum partly broken away and with some of the individual members removed;

FIG. 6 is a detail view in section along the line VIVI of FIG. 5; and

FIG. 7 is a fragmentary diagrammatic view of another embodiment.

SPECIFIC DESCRIPTION In FIG. 1 of the drawing, there is shown a digital clock in which units 1, 2 and 3, in the form of drum arrangements, are rotatably mounted in a housing 4 to display, respectively, the seconds, minutes and hours; the display arrangements 1 and 2 each consist of a pair of drums 1a, 2a and 1b, 2b respectively carrying the units and tens indicia. The numerals carried by drum 1a and drum 2a run from 0 to 9 while the numerals carried by drums 1b and 2b run from 0 to 5. Hence the units 1 and 2 each may display numerals running from 00 to 59.

A single drum is represented at 3, however, for displaying all 24 of the hour numerals '(1. 24 or 00 23 as the case may be). The housing 4 is provided with a frame 6 enclosing a window 6a through which the numerals may be observed from the exterior. The viewing direction is represented at B in FIG. 3. The frame 6 is formed with sides which converge inwardly toward the drums to mask indicia thereon other than that which is to be displayed. The drum arrangements 1, 2 and 3 are here shown to be provided with a common axis 5 and to be driven by a stepping arrangement represented diagrammatically at D in FIG. '1 such that the drum 1a is stepped through 360 or a full revolution in increments of one second in a total period of 10 seconds, the drum 1b is stepped through 360 in increments of 10 seconds over a total period of 60 seconds, the drum 2a. is stepped through 360 in increments of one minute over a total period of 10 minutes and the drum 2b is stepped through 360 in increments of 10 minutes over a total period of one hour. The drum 3, however, is connected to the drive D so as to be stepped through 360 over a period of 8 hours in increments of one eighth revolution. The operation of the minute and second drums 1, 2 is, of course, conventional and needs no further elucidation.

In FIG. 3, we have illustrated the details of the present invention insofar as it applies to the display of a 24-hour period in a 24-hour clock. The 24-hour drum comprises, about the axis 8, eight small polygonal display members 9 of equilateral-triangular cross section, each rotatable about an axis 10 lying along an imaginary circle 10a centered about axis 8. The members 9 are angularly equispaced through angles a, where The drum 7 is, in turn, stepped in one-hour intervals through angular increments of u.

The three-sided members 9 are provided along their broad flanks with numerals or digits representing the hours and illustrated at 9a in FIG. 3A so that, upon alignment of, for example, the broad flanks 9b with the window 6a in FIG. 3, the numeral 7 is displayed. In three full revolutions of the drum 7, all of the numerals carried by the surfaces 9a, 9b, will register with the window 60, each for a period of one hour, over 24 hours.

Each of the individual members 9 carries three numerals upon its sides in accordance with the relationship N=n, n+b, n+2b where N is the displayed numeral, n is the lowest numeral value of the particular member and b is the number of members provided along the drum, 11:1, b or 11:0, b-l. The lower numeral recorded at each of the members 9 of the drum will increase counter to the direction of rotation of the drum so that successive members in the counterclockwise sense bear the numeralsl 8 or 0 7respectively. The numbering sequence for the drums is illustrated in FIG. 3 and in the following table:

and 9d and is rotated through an 5 while the drum 7 is stepped in angular increments 1O for each hour and four complete revolutions of the drum 7 is required in each 24-hour period. It will be understood that, while systems with b=8 and :3 have been found to be preferable, units such as that illustrated in FIG. 7 in which six individual display drums, each having four display numerals, may also be desirable and that the invention may be extended to more complex arrangements permitting the display of substantially any number a of digits as long as a=b x c. In the system of FIG. 7, of course, the individual drums 9' are of square "cross section and represent rectangular parallelepipeds. It will be apparent from the principles illustrated in FIGS. 3 and 3a that for any given height of numerals, the drum of the present invention may be one third the diameter of the drum upon which the numerals are all displayed simultaneously. With 24 numerals and c=3, the diameter may be as small as In FIGS. 4-6, we have illustrated the mounting of the individual drums 9 in somewhat greater detail.

According to a specific feature of this invention the carrier drum 7 (see especially in FIG. 5) is injectionmolded in a single piece of synthetic resin (unitarily or monolithically) with a core 8 and a pair of transverse flanges 11 and 12 formed with circular arrays of bores 14 angularly equispaced about the axis 5 at the aforementioned angles a. The bores 14 are dimensioned to receive studs 13 formed on the axially opposite ends of the polygonal bodies 9 which, in turn, are injection-molded in one piece from a synthetic resin as well. The thickness T of the flanges 11 and 12, in the axial direction, is equal to or less than 2!, Where t is equal to the axial length of the individual studs 13. Consequently, each stud 13 has an axial length twhich is at most equal to T/ 2.

The studs are received in the bores 14 so as to be freely rotatable therein. Between the end. faces 9z and 9y, and the faces 11a and 12a of the flanges 11 and 12, the polygonal bodies 9 are unitarily provided with cylindrical spacer bosses 30 or spacer washers which may be mounted upon the studs 13. The spacer members 30 may be composed of a low-friction material, e.g. polytetrafluoroethylene, or may be coated therewith to limit frictional adhesion of the numeral-bearing bodies 9 to the carrier drum 7.

Flange 11 is formed with an axially extending cylindrical apron 16 projecting outwardly from the disk-shaped portion of this flange, and formed preferably internally, with indexing formations which can cooperate with a stepping pawl or other drive means (not shown) adapted to index the drum through the angle a upon the lapse of each hour.

Flange -12 is, in turn, rotatable within a fixed cylindrical sleeve or housing 17 which comprises a disk-shaped 7O portion 17a and a cylindrical apron 19 carrying a stepping pawl best seen in FIG. 4. The apron 19 overhangs the end portion of the numeral drums 9 which have cutaway corners as represented at 20 so that, once the drums 9 are passed the turning region, illustrated as a cutout 24 along the apron, they are retained in their original angular orientation against further rotation by the inner surface 19a of the apron. The cutaway corners and limited width of the surfaces 22, permits the total width W of the polygonal surfaces 21 to the maximalized without interference between the bodies 9.

The pawl comprises a cowling in the form of an extension 27 of the apron 19 so that a downwardly projecting finger lies in the path of the edges 23 of the numeralcarrying drums 9 as best seen in FIGS. 4 and 6. As the edge 23 of a previously viewed drum 9 is entrained in the clockwise sense (FIG. 4) into engagement with the projection 25 of pawl 26, it is rotated in the counterclockwise sense (FIG. 6) through 120 until it is guided along the extension 27 and eventually is held by the apron 19 beyond the step 28. The pawl 26 thus functions as a stepping tooth capable of rotating each of the numeral-display wheels 9 to turn under the previously exposed numeralcarrying surface. The extension 27 of the apron 19 runs in a spiral arc approximately tangential to the path of the drum 7 and terminates at the step 28 at which the slender apron portion 19, set back from the edge 27 of the extension cooperates with the flanks 22 between the cutaway corners to guide the individual numeral-carrying drum. In other words, at the opening 24, the radial distance of the cowling 27 from the drum is greater than at 28 and the cowling thus guides the broad surfaces of the polygons until, at 28, the narrower apron 19 becomes effective to cooperate with surface 22 between rounded corners.

It will be appreciated that, while drum pairs 1 and 2 have been used to indicate the minutes and seconds, it is possible to use a single drum for this purpose, in which case, for the indication of numerals, a 3-sided numeralcarrying drum may be employed and 20 of them are angularly spaced about the carrier. It is also understandable that the invention may be used to display indicia other than numerals, that the numerals sequence need not be decadic and that many more than eight individual numeral-carrying drums may be provided, e.g., up to about 48.

The improvement described and illustrated is believed to admit of many modifications within the ability of persons skilled in the art, all such modifications being considered within the spirit and scope of the invention except as limited by the appended claims.

We claim:

1. In a direct-reading clock having a housing provided with a window, and an indicator device for displaying at least hour numerals, the improvement wherein said device comprises:

a drum unitarily molded from a synthetic resin and having a central shaft portion and a pair of flange portions at opposite ends of said shaft portion, at least one of said flange portions being resiliently deflectable;

eight elongated bodies of triangular cross section and provided with aligned studs at opposite ends of each body, said bodies being angularly equispaced about said drum and rotatably mounted between said flange portions thereof with said studs being receivable in said flange portions, each of said bodies having three angularly offset principal faces bearing respective numerals visible through said window upon the stepping of said drum therepast;

a stationary generally cylindrical apron axially overhanging one end of said drum in the path of said bodies, said bodies each having a reduced end portion stepped inwardly by an amount corresponding approximately to the thickness of said apron and slidably engaging same for maintaining the angular orientation of said bodies during at least a major portion of each revolution of said drum, said apron being interrupted at a limited region of the path of 8 said drum to enable rotation of each body at said References Cited a iii-33315 23 323 ;$21 53; ggii l iid a eab1e UNITED STATES PATENTS with each body in turn as it enters said region for 2,154,495 4/1939 Dahlberg 235 11 rotating the body through one third of a revolution. 5 2'154495 4/1939 Dahlberg 235 1 2. The improvement defined in claim 1 wherein said 3,223,320 12/1965 Bea-Ft 235 108 apron forms part of a cup-shaped housing enclosing said 3245I616 4/1966 Hemngton 235 72 one of said flange portions of said drum. 3,263,920 8/1966 Reed 235-117 3. The improvement defined in claim 2 wherein said bodies are formed unitarily with said studs from a syn- 10 RICHARD WILKINSON Pnmary Examiner thetic resin, said flange portions have thicknesses T 22L A-WAL,A$SiStaI1tEXaII1iI1r where t is the axial length of said studs, each of said bodies being further provided with a cylindrical boss at each end thereof, from which the respective stud projects. 582, 126 E; 2351 C, 72, 117 

